Bicycle gear set

ABSTRACT

A bicycle gear assembly has first and second sets of cogwheels, each having at least three cog wheels of various sizes including a largest cogwheel and a smallest cogwheel. These two sets are oriented so that the largest cogwheel of the first set is aligned with the smallest cogwheel of the second set and the smallest cogwheel of the first set is aligned with the largest cogwheel of the second set, the first and the second sets of cogwheels define at least a first, second and third pair of substantially aligned cogwheels. Additionally, a chain is mounted about a first pair of the aligned cogwheels and a gear shift assembly is adapted to move the chain from the first pair of cogwheels to the second pair of cogwheels and from the second pair of cogwheels to the third pair of cogwheels.

BACKGROUND OF THE INVENTION

Since the advent of mountain biking, there has been a perceived need fora bicycle gearing system that both is resistant to being derailed bydebris that is accidentally kicked up into the gear set by a bicyclerider and yet offers a wide range of gearing. Toward this goal gearingsystems have appeared in the literature, in which the gears are encasedin a protective housing.

In these new systems a drive wheel may be co-journalled with a drivenset of gears and, in turn, drive a cogwheel on the bicycle's rear wheel.Unfortunately, these systems do not have as wide a range of gearingoptions as some mountain biking enthusiasts might desire. Moreover, theinner workings of some gear box designs are fairly complicated,resulting in a gear box that is heavier and more prone to largerfrictional losses and rapid wear than is desirable.

SUMMARY

The following embodiments and aspects thereof are described andillustrated in conjunction with systems, tools and methods which aremeant to be exemplary and illustrative, not limiting in scope. Invarious embodiments, one or more of the above-described problems havebeen reduced or eliminated, while other embodiments are directed toother improvements.

In a first separate aspect, the present invention is a bicycle gearassembly that comprises first and second sets of at least threeco-journalled cogwheels, each having co-journalled cogwheels of varioussizes including a largest cogwheel and a smallest cogwheel. These twosets are oriented so that the largest cogwheel of the first set issubstantially aligned with the smallest cog wheel of the second set andvice versa. Accordingly, the first and the second sets of cogwheelsdefine at least a first, second and third pair of substantially alignedcog wheels. Additionally, a chain is mounted about a first pair of thealigned cogwheels and a gear shift assembly is adapted to move the chainfrom the first pair of substantially aligned cogwheels to the secondpair of substantially aligned cogwheels and from the second pair ofsubstantially aligned cogwheels to the third pair of substantiallyaligned cogwheels.

In a second separate aspect, the present invention is a bicycle thatincludes a gear assembly that has first and second sets of co-journalledcogwheels, each having at least three cogwheels of various sizesincluding a largest cogwheel and a smallest cogwheel, oriented so thatthe largest cogwheel of the first set is aligned with the smallestcogwheel of the second set and vice versa. Accordingly, the first andthe second sets of cogwheels define at least a first, second and thirdpair of substantially aligned cogwheels. Additionally, a chain ismounted about a first pair of aligned cogwheels and a gear shiftassembly is adapted to move the chain from the first pair ofsubstantially aligned cogwheels to the second pair of substantiallyaligned cogwheels and from the second pair of substantially alignedcogwheels to the third pair of substantially aligned cogwheels.

In a third separate aspect, the present invention is a gear assembly,comprising a co-journalled set of drive cogwheels and a co-journalledset of driven cogwheels. Also, a circular chain links a drive cogwheelto a driven cogwheel. Finally, a chain tensioning assembly includes apolymeric roller that defines a channel on its outer rim and isrotationally mounted on a tensioned arm that pushes this polymericroller into the chain. This assembly is positioned so that the chainresides in the roller rim channel.

In addition to the exemplary aspects and embodiments described above,further aspects and embodiments will become apparent by reference to thedrawings and by study of the following detailed descriptions.

BRIEF DESCRIPTION OF THE DRAWINGS

Exemplary embodiments are illustrated in referenced figures of thedrawings. It is intended that the embodiments and figures disclosedherein are to be considered illustrative rather than restrictive.

FIG. 1 is a partial side view of a bicycle, including a gear box as inthe present invention.

FIG. 2 is a downwardly looking sectional view taken along lines 2-2 ofFIG. 1.

FIG. 3 is a sectional side view taken along line 3-3 of FIG. 2.

FIG. 4 is a detail sectional side view, taken along line 4-4 of FIG. 2.

FIG. 5 is a detail sectional side view, taken along line 5-5 of FIG. 2.

FIG. 6 is a sectional side view, taken along line 6-6 of FIG. 2.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

Referring to FIG. 1, a bicycle 10 includes a preferred embodiment of abicycle gear assembly 11. Turning to FIG. 2, assembly 11 includes aco-journalled drive cog wheel set 12, a co-journalled driven cogwheelset 14 and a chain 16 linking a cogwheel on set 12 with a cogwheel onset 14. Drive set 12 is driven by a pair of pedals 18 (FIG. 1) anddriven set 14 is driven by way of chain 16, from set 12. Referring againto FIG. 1, the driven set 14, is co-journalled to a stand alone drivecogwheel 20 that powers a chain 22 that, in turn, powers a bicycle rearwheel 24 by way of a rear wheel cogwheel 26.

A tension roller 30, preferably made of durable polymer and having anouter rim that defines a channel or groove for accepting the chain 16,is mounted on a roller arm 32 that is spring loaded to press roller 30inwardly into chain 16. This causes a greater engagement of chain 16with the teeth of the cogwheels about which it is mounted. The moreteeth are engaged with chain 16, the more force may be transmitted fromcogwheel set 12 to set 14. Also, the tension roller 30 serves thepurpose of taking up the extra chain length that is necessary to allowthe chain to successfully transit from one cogwheel to the next cogwheel and that accommodates the small changes in chain slack as thegears are changed in steps, as described below.

Referring to FIGS. 2, 4 and 5, to effect a shifting of gears, a cable 34is pulled so that it rotates a guide bar 36. A set of chain shiftchannels 38 and a driven cog set shift channel 39, move a chain shiftguide bar follower 40 and driven cog set shift guide bar follower 42,which move the chain 16 and the driven cogwheel set 14 respectively inresponse to the rotation of guide bar 36. A pair of slide rods 41prevent follower 40 from rotating about guide bar 36. Skilled personswill recognize that a bearing/coupling must be used to join follower 42and the largest of cogwheels 14 so that as follower 42 operativelypresses against this cogwheel 14 it does not impede its rotation by wayof frictional resistance. The bearing/coupling also makes it possiblefor follower 42 to move cogwheel set 14 by pulling on it transversely.Bearing/coupling devices are well known in the art.

To facilitate their movement, a pair of ball bearing sets 44 are mountedin followers 40 and 42 and set into guide bar channels 38 and 39,respectively, to facilitate movement of followers 40 and 42. The chainshift guide bar follower 40 includes an upper chain cage 46 (FIG. 6) anda lower chain cage 48 (FIG. 6). Cage 46 surrounds the upper (loaded) runof chain 16 whereas cage 48 surrounds the lower (non-loaded) run ofchain 16. Cages 46 and 48 provide the sideways loading on the chain 16necessary to force gear changes on both cog gear sets.

Facing in the direction of FIG. 3, a counterclockwise rotation of guidebar 36, causes the chain 16 to be moved into the paper. As the gear set11 is shifted from the highest gearing, which is shown in FIGS. 2, 3 and6, to the lowest gearing (not shown), chain 16 is shifted in alternatingstep types. In a first step type the chain is shifted from a smallerdriven cogwheel 14 to a larger driven cogwheel 14, whereas in a secondstep type the chain is shifted from a larger drive cogwheel 12 to asmaller drive cogwheel 12.

In greater detail in the first step type, as dictated by driven setchannel 39, the driven cogwheel set 14, following the back and forthpattern of channel 39 moves in the “out of the paper” (of FIG. 3)direction while chain 16 is kept stationary in the transverse dimensionas guide bar channels 38 are straight in this interval. As notedpreviously, in this first step type chain 16 moves from a smaller drivencogwheel 14 to a larger driven cog wheel 14. In the second step type,the driven wheel set 14, now reversed in direction due to the back andforth pattern of channel 39, is moved in tandem with the chain shiftguide bar follower 40 and chain 16. This is because the portions of thechain shift channels 38 and the driven set channel 39 that run in thesame helical pattern are now being used to move followers 40 and 42,respectively. As a result, upper cage 46 pushes the chain 16 to movefrom a larger drive cogwheel 12 to a smaller drive cogwheel 12. Byrepeating the first step and the second step type the chain 16 can bemoved in steps and may be changed from the two highest gearing cogwheelsof sets 12 and 14 to the two lowest gearing cogwheels of sets 12 and 14.The reverse process takes place when shifting from lowest gear tohighest gear.

A spline 50 permits cogwheel 14 to be moved transversely back and forthand yet drive an axle 52, which is journalled to and drives drivecogwheel 20 (FIG. 1). A one way clutch 54 permits the rotation of drivecogwheel set 12 while the pedals 18 are stationary. A sturdy housing 60of metal (steel or aluminum, for example) or a robust polymer protectsgear box 11 from an intrusion of debris.

Skilled persons will appreciate that although cog wheel sets 12 and 14are shown as being identical but rotated 180 degrees relative to eachother, these sets need not be identical. In one preferred embodiment,each substantially aligned pair of cogwheels (one cogwheel from set 12and the other from set 14) collectively has the same number of teeth asall the other substantially aligned cogwheel pairs. Although in otherpreferred embodiments this is not the case, there is an advantage forthe case in which each aligned cogwheel pair collectively has a numberof teeth that is not very different from the other, similar, alignedcogwheel pairs. The advantage is that a single tension roller 30, whichprovides more chain wrap on both cogs, is possible since in thisembodiment the change in chain slack over the gearing range is small.

While a number of exemplary aspects and embodiments have been discussedabove, those skilled in the art will recognize that it would be possibleto make certain modifications, permutations, additions andsub-combinations thereof. It is therefore intended that the followingappended claims and claims hereafter introduced are interpreted toinclude all such modifications, permutations, additions andsub-combinations as are within their true spirit and scope.

1. A bicycle gear assembly, comprising: (a) first and second sets ofco-journalled cog wheels, each having at least three cogwheels ofvarious sizes including a largest cog wheel and a smallest cogwheel,oriented so that said largest cogwheel of said first set is aligned withsaid smallest cogwheel of said second set and said smallest cogwheel ofsaid first set is aligned with said largest cogwheel of said second set,said first and said second sets of cogwheels defining at least a first,second, and third pair of aligned cogwheels; (b) a chain mounted aboutone of said pairs of aligned cogwheels; (c) a gear changing assemblyadapted to move said chain from said first pair of aligned cogwheels tosaid second pair of aligned cog wheels, and from said second pair ofaligned cogwheels to said third pair of aligned cogwheels.
 2. The gearassembly of claim 1 further comprising a housing protecting said chainand said cogwheels.
 3. The gear assembly of claim 1, said assembly beingmounted on a bicycle and wherein a drive gear is co-journalled to saidsecond gear set, said drive gear being fitted with a chain to drive acogwheel co-journalled to a wheel of said bicycle.
 4. The gear assemblyof claim 1, wherein each of said sets of cogwheels is identical.
 5. Thegear assembly of claim 4, wherein each of said sets of cogwheels havecogwheels arranged linearly, in order of increasing size.
 6. The gearassembly of claim 1, wherein chain defines a closed form defining anoutside region and an inside region and said gear change assemblyincludes a chain tensioning roller located in said outside region,adapted to press against said chain pushing said chain toward saidinside region, to place tension on said chain.
 7. The gear assembly ofclaim 6, wherein said chain tensioning roller presses on said chaintoward said inside region at a location between said cogwheel sets,thereby causing a greater engagement of said chain with said cogwheels.8. The gear assembly of claim 1 wherein said gear change assembly movessaid chain from a first pair of aligned cogwheels to a second pair ofaligned cogwheels by first moving said chain to a first one of saidsecond pair of aligned cogwheels and then moving the chain to a secondone of said second pair of aligned cogwheels.
 9. The gear assembly ofclaim 8 wherein said gear assembly may be used to transmit torquebetween said two sets of cogwheels, without causing a further gear shiftafter said chain has been moved to said first one of said second pair ofaligned cogwheels and before said chain has been moved to said secondone of said second pair of aligned cogwheels.
 10. The gear assembly ofclaim 1 wherein said cogwheel sets are moved transversely relative toone another to effect cogwheel alignment at every gearing.
 11. Abicycle, comprising: (a) a gear assembly, having: (i) first, and secondsets of co-journalled cogwheels, each having cogwheels of various sizesincluding a largest cog wheel and a smallest cogwheel, oriented so thatsaid largest cog wheel of said first set is aligned with said smallestcogwheel of said second set and vice versa, said first and said secondsets of cogwheels defining at least a first, second and third pair ofaligned cogwheels; (ii) a chain mounted about a first pair of alignedcogwheels; (iii) a gear changing assembly adapted to move said chainfrom said first pair of aligned cogwheels to said second pair of alignedcogwheels and from said second pair of aligned cogwheels to said thirdpair of aligned cog wheels.
 12. The bicycle of claim 11 furthercomprising a housing protecting said chain and said cog wheels.
 13. Thebicycle of claim 11 wherein a drive gear is co-journalled to said secondgear set, said drive gear being fitted with a chain to drive a cogwheelco-journalled to a wheel of said bicycle.
 14. The bicycle of claim 11wherein each of said sets of cogwheels is identical.
 15. The bicycle ofclaim 11 wherein each of said sets of cogwheels have cogwheels arrangedlinearly, in order of increasing size.
 16. The bicycle of claim 11wherein said gear change assembly includes a chain tensioning roller,adapted to press inwardly against said chain, to place tension on saidchain.
 17. The bicycle of claim 11 wherein said gear change assemblymoves said chain from a first pair of aligned cogwheels to a second pairof aligned cogwheels by first moving said chain to a first one of saidsecond pair of aligned cogwheels and then moving the chain to a secondone of said pair of aligned cogwheels.
 18. The gear assembly of claim 17wherein said gear assembly may be used after said chain has been movedto said first one of said second pair of aligned cogwheels but beforesaid chain has been moved to said second one of said pair of alignedcogwheels.
 19. The gear assembly of claim 11 wherein said cogwheel setsare moved transversely relative to one another to effect cogwheelalignment at every gearing.
 20. A gear assembly, comprising: (a) aco-journalled set of drive cogwheels; (b) a co-journalled set of drivencogwheels; (c) a circular chain linking a drive cogwheel to a drivencogwheel; and (d) a chain tensioning assembly comprising a polymericroller defining a channel on its outer rim, and rotationally mounted ona tensioned arm that pushes said polymeric roller into said chain andpositioned so that said chain resides in said channel.
 21. The gearassembly of claim 10, wherein each said cogwheel set defines acogwheel-to-cogwheel spacing and said relative movement of said cogwheelsets is limited to one cogwheel-to-cogwheel spacing.